Minghua Liu

Covalent Triazine-Based Frameworks as Visible Light Photocatalysts for the Splitting of Water.

Covalent triazine-based frameworks (CTFs) with a graphene-like layered morphology have been controllably synthesized by the trifluoromethanesulfonic acid-catalyzed nitrile trimerization reactions at room temperature via selecting different monomers. Platinum nanoparticles are well dispersed in CTF-T1, which is ascribed to the synergistic effects of the coordination of triazine moieties and the nanoscale confinement effect of CTFs. CTF-T1 exhibits excellent photocatalytic activity and stability for H2 evolution in the presence of platinum under visible light irradiation (λ ≥ 420 nm). The activity and stability of CTF-T1 are comparable to those of g-C3 N4 . Importantly, as a result of the tailorable electronic and spatial structures of CTFs that can be achieved through the judicial selection of monomers, CTFs not only show great potential as organic semiconductor for photocatalysis but also may provide a molecular-level understanding of the inherent heterogeneous photocatalysis.

Photocatalytic reduction of CO2 with H2O to CH4 over ultrathin SnNb2O6 2D nanosheets under visible light irradiation

Monolayer SnNb2O6 two-dimensional (2D) nanosheets with high crystallinity are prepared by an one-pot and eco-friendly hydrothermal method without any organic additives. For the first time, these SnNb2O6 nanosheets are applied to the photocatalytic reduction of CO2 with H2O to CH4 in the absence of co-catalysts and sacrificial agents under visible light irradiation. The structural features, morphology, photoabsorption performance, and photoelectric response have been investigated in detail. Results show the as-prepared SnNb2O6 samples with typical 2D nanosheets in the thickness of about 1 nm. Owing to the unique features of the nanosheets, the surface area, photoelectrical properties and the surface basicity of SnNb2O6 are greatly improved compared with the counterpart prepared by traditional solid state reaction. Furthermore, the adsorption capacity of CO2 on SnNb2O6 nanosheets is much higher than that of layered SnNb2O6. Thus, the photocatalytic activity of SnNb2O6 nanosheets for the reduction of CO2 is about 45 and 4 times higher than those of the references (layered SnNb2O6 and common N-doped TiO2), respectively. To understand the interactions between the CO2 molecule and the surface of the photocatalyst, and the reactive species in the reduction process, the intermediates have also been detected by in situ FTIR with and without visible light irradiation. Finally, a possible mechanism for the photocatalytic reduction of CO2 with H2O to CH4 on SnNb2O6 nanosheets is proposed. We believe this work will provide new opportunities for expanding the family of visible-light driven photocatalysts for the reduction of CO2.

Design and Synthesis of TiO2 Hollow Spheres with Spatially Separated Dual Cocatalysts for Efficient Photocatalytic Hydrogen Production

TiO2 hollow spheres modified with spatially separated Ag species and RuO2 cocatalysts have been prepared via an alkoxide hydrolysis–precipitation method and a facile impregnation method. High-resolution transmission electron microscopy studies indicate that Ag species and RuO2 co-located on the inner and outer surface of TiO2 hollow spheres, respectively. The resultant catalysts show significantly enhanced activity in photocatalytic hydrogen production under simulated sunlight attributed to spatially separated Ag species and RuO2 cocatalysts on TiO2 hollow spheres, which results in the efficient separation and transportation of photogenerated charge carriers.

Cellulose/SnS2 composite with enhanced visible-light photocatalytic activity prepared by microwave-assisted ionic liquid method

A facile method was used to synthesize cellulose/SnS2 composites (CE/SnS2) by a microwave-assisted ionic liquid (MAIL) method. The effects of ionic liquid types on the structure and properties of SnS2 samples were investigated. Results showed that the ionic liquid played an important role in the control over the morphology, size and photocatalytic performance of the SnS2 particles. The as-synthesized CE/SnS2 composites were systematically investigated by XRD, SEM, TEM, BET, XPS, UV-visible and PL. It was demonstrated that the obtained CE/SnS2 composites showed three-dimensional architecture and excellent visible-light photocatalytic activity as photocatalyst for RhB degradation. The superior visible-light photocatalytic performances for composites were ascribed to their composite structure and the synergistic effects between flower-like SnS2 and cellulose.

Trichloroacetic Acid Removal by a Reductive Spherical Cellulose Adsorbent

A novel spherical cellulose adsorbent with amide and sulphinate groups was used for a first reduction of trichloroacetic acid(TCAA) and a subsequent adsorption of generated species, haloacetic acids. The removal mechanism involved TCAA reduction by sulphinate groups and the adsorption of the haloacetic acids through electrostatic interaction with amide group. Investigation of product formation and subsequent disappearance reveals that the reduction reactions proceed via sequential hydrogenolysis, and transform to acetate ultimately. Adsorption of haloacetic acids was ascertained by low chloride mass balances(89.3%) and carbon mass balances(75.1%) in solution. The pseudo-first-order rate constant for TCAA degradation was (0.93±0.12) h–1. Batch experiments were conducted to investigate the effect of pH value on the reduction and adsorption process. The results show that the reduction of TCAA by sulphinate groups requires higher pH values while the electrostatic attraction of haloacetic acids by amino group is favorable in more acidic media.

Surfactant-assisted hydrothermal synthesis of rGO/SnIn4S8 nanosheets and their application in complete removal of Cr(VI)

To solve the problem of contamination of hexavalent chromium (Cr(VI)), visible-light-driven graphene-based ternary metal chalcogenide nanosheets (rGO/SnIn4S8) were synthesized via a one-pot surfactant-assisted hydrothermal method for the photoreduction of Cr(VI). Characterizations demonstrated that SnIn4S8 nanosheets were uniformly distributed on the surface of rGO and the as-synthesized nanosheets exhibited excellent photocatalytic activity under visible light. In addition, the effects of pH, concentration of critic acid, holes and electron scavengers on the reduction of Cr(VI) were systematically investigated. It was found that 50 mg L−1 of Cr(VI) could be completely removed within 30 min at pH 2 when citric acid served as a hole scavenger. Kinetic studies showed that the photocatalytic reduction of Cr(VI) processes obeyed the pseudo first order model. Further study indicated that the Cr(III) species was immediately adsorbed onto the surface of the rGO/SnIn4S8 nanosheets after photocatalytic reduction of Cr(VI). Additionally, recycling results suggested that rGO/SnIn4S8 nanosheets possessed high recycle ability and stability after repeated use (5 times). This effective and promising work might provide a new strategy for the photoreduction of Cr(VI) and complete removal of chromium from effluent through the novel photocatalyst rGO/SnIn4S8.

One-Pot Hydrothermal Synthesis, Characterization, and Desulfurization Performance of ZnFe2O4/AC Composites

ZnFe2O4/AC composites were prepared by the one-pot hydrothermal method using the activated carbon (AC) as a carrier. The synthesis conditions were optimized by a single-factor experiment. The structural, textural, and surface properties of the adsorbent have been comprehensively characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, Brunauer–Emmett–Teller (BET) measurements, and X-ray photoelectron spectroscopy (XPS) analysis. The SO2 removal capacities of the composites were investigated via testing the adsorption capacity at the self-made desulfurization equipment. The results show that the adsorption capacity of ZnFe2O4/AC composites is much higher than that of the AC and ZnFe2O4 samples, respectively. The composite overcomes the disadvantages of the traditional sintering, showing a very high desulfurization performance. The breakthrough time was 147u2009min, and the sulfur adsorption capacity could reach 23.67% in the desulfurization performance test.

Macromol. Rapid Commun. 20/2015

Frontispiece: A covalent triazine-based framework (CTF) possessing a graphene-like layered morphology demonstrates excellent photocatalytic activity and stability in splitting water under visible light irradiation. Due to the tailorable electronic and spatial structures of CTFs, they not only show great potential as organic semiconductors for photocatalysis but also provide a molecular-level understanding of the inherent heterogeneous photocatalysis. Further details can be found in the article by J. Bi,* W. Fang, L. Li, J. Wang, S. Liang, Y. He, M. Liu, and L. Wu* on page 1799.